As for the synthetic method for substituted triazine derivatives, various synthetic methods have heretofore been known. For example, it has been reported a synthetic method for those compounds of the formula (III) ##STR1## wherein X.sup.4 and X.sup.5 represent each a diethylamino group, and X.sup.6 represents an ethylamino group, or X.sup.4 and X.sup.5 represent each an amino group, and X.sup.6 represents an ethylamino group or a diethylamino group, which method includes the reaction of 2-chloro-1,3,5-triazine derivative with ethylamine (J. Amer. Chem. Soc., vol. 73, p.2984 (1951)). Those compounds of the formula (III) wherein X.sup.4, X.sup.5 and X.sup.6 represent each an ethylamino group have been reported by a synthetic method which includes reacting 2,4,6-trimethylthio-1,3,5-triazine with ethylamine (Chem. Ber., vol. 18, p.2755 (1885)). Those compounds of the formula (III) wherein X.sup.4 represents an amino group, X.sup.5 represents an amino group or an octylamino group, and X.sup.6 represents an octylamino group have been reported by a synthetic method which includes reacting 2,4,6-triamino-1,3,5-triazine with octylamine hydrochloride (U.S. Pat. No. 2,228,161 (1941)).
Those compounds of the formula (III) wherein X.sup.4 represents a phenyl group and X.sup.5 and X.sup.6 represent each a butylamino group have been reported by a synthetic method which includes reacting 2-phenyl-4,6-diamino-1,3,5-triazine with butylamine (U.S. Pat. No. 2,385,766 (1945)).
Particularly, in recent years, development of compounds introduced with a substituent having a hydroxyl group is becoming increasingly active. For example, there is a description of a compound of the formula (VI) ##STR2## having carcinostatic activity (U.S. Pat. No. 5,534,625 (1996)).
Further, it has been reported that compounds of the formula (VII) ##STR3## are useful as an aminoplast modifier (U.S. Pat. No. 4,668,785. (1987)).
Heretofore, various synthetic methods have been studied for synthesizing these compounds. For example, for the compounds of the formula (VI), there is a report of addition reaction between an N-substituted triazine derivative and formalin (U.S. Pat. No. 5,534,625 (1996).
Furthermore, for the N-substituted triazine derivatives of the formula (VII) having hydroxyethyl groups as a substituent, there is a report of transamination reaction between melamine and ethanolamine (U.S. Pat. No. 4,668,785 (1987)). Similarly, transamination reaction between melamine and isopropanolamine is also reported (U.S. Pat. No. 4,618,676 (1986)).
Also, development has been under way of synthetic methods which catalytically produce various new N-substituted triazine derivatives, such as a method for preparing N-substituted triazine derivatives from a 1,3,5-triazine. derivative, typically melamine, as a starting material and an alcohol proposed by the present inventors (WO 95/03287 (corresponding to JP-A-8-27128)), a method for preparing N-substituted triazine derivatives from an aldehyde and a ketone (WO 95/30662 (corresponding to JP-A-8-193071)), and a method for preparing N-substituted triazine derivatives from an olefin (JP-A-8-27125).
The synthetic method disclosed in J. Amer. Chem. Soc. vol. 73, p.2984 (1954) in most cases needs at least equimolar amount of a condensing agent and generates by-products, such as salts, which would often cause problems in industry. The synthetic method described in Chem. Ber., vol. 18, p.2755 (1885) generates by-products, such as sulfur compounds, which would often cause problems in industry. The synthetic methods disclosed in U.S. Pat. Nos. 2,228,161 and No. 2,385,766, respectively, need high temperatures for reaction and the former by-produces ammonium chloride. It is common in these cases that substitution reaction of releasable groups is performed with substituted amines, which are not inexpensive industrially. This is one of the reasons that prevent N-substituted triazines from being available at low costs.
The method described in U.S. Pat. No. 5,534,625, which is a formalin addition reaction known in the art, is in itself an equilibrium reaction and, hence, the product is obtained in the form of equilibrium composition, so that the yield of the intended compound is not always high.
The methods described in U.S. Pat. Nos. 4,668,785 and No. 4,618,676 are very excellent for introducing hydroxyethyl groups or the like though they involve reactions at high temperatures with acid catalysts. However, when it is attempted to introduce various substituents, the methods are not so suitable since raw materials that are available are restricted and kinds of compounds which can be supplied on an industrial scale at low costs are limited.
It is easy to suppose that in order to incorporate such substituents at a lowest possible cost, it is desirable to use an oxirane derivative or an ethylene glycol derivative (inclusive of oligoethylene glycol) as a raw material. However, there is a report that in the reaction between ethylene oxide and melamine, for example, ring opening addition reaction after the addition reaction with melamine is difficult to control so that the introduction of a polyethylene glycol chain cannot be prevented (J. Appl. Polym. Soc., vol. 58, p.559 (1995)). At present, no satisfactory synthetic method has been known.
Further, the synthetic method for catalytic synthesis of N-substituted triazine derivatives proposed by the present inventors is a manufacturing method which is excellent in that it is conducted industrially at low costs. However, even the method using aldehyde, ketone or the like, which method is considered to be most versatile and excellent among the above-described methods in view of the variety in kind and amount of products and controllability of side reactions, can not to be an ideal one from the viewpoint of process economy because the method involves use of raw materials which has high oxidizability and combustibility and the combination of raw materials having high oxidation degree and reduction conditions. With respect to the introduction of substituents having a hydroxyl group, a modification reaction with an alcohol which can use ethylene glycol derivatives (oligo ethylene glycol or the like) which are available at low costs on an industrial scale is considered suitable. However, in the above-described method which prepares N-substituted triazine derivatives using alcohols (WO95/03287 corresponding to JP-A-8-27128)), the reaction with a dihydric alcohol is not always satisfactory in selectivity, yield, and the like. Accordingly, there is a demand for developing a synthetic method for preparing N-substituted triazine derivatives which has high generality and is excellent from industrial viewpoints.
On the other hand, N-substituted melamine derivatives are compounds which are useful as intermediates for medicines and agricultural chemicals and which are utilized in resin-related fields, such as coatings, adhesives, molding materials, flame retarding materials, and the like based on their excellent characteristics such as reactivity, solubility in solvents, and heat resistance. For example, various 2,4,6-substituted melamine derivatives synthesized from cyanuric chloride can be used as a flame retardant for thermoplastic polymers as described in JP-A-3-215564. Some specific examples described therein are shown below. ##STR4##
As a result of intensive investigation with view to solving the above-described problems, the present inventors have completed a first invention directed to a method including reacting various alcohols, which are available at low costs on an industrial scale, with an amino group or a mono-substituted amino group on a triazine ring in the presence of a metal catalyst and hydrogen to introduce an alkyl group or an alkenyl group into the amino group or the mono-substituted amino group in high yields, with generating only water as a by-product. Similarly, the present inventors have completed a second invention directed to a method including reacting various ethylene glycol derivatives (oligo ethylene glycol and the like), which are available at low costs on an industrial scale, with an amino group or a mono-substituted amino group on a triazine nucleus in the presence of a metal catalyst and hydrogen to introduce an alkyl group having a terminal hydroxyl group into the amino group or the mono-substituted amino group in high yields, with generating only water as a by-product.
The substituted 1,3,5-triazine derivatives obtained by these reactions considerably inhibit the multimolecular association through intermolecular hydrogen bonding which aminotriazines inherently have and, hence, the derivatives have increased solubilities in various solvents and at the same time decreased melting points, so that their compatibility with other organic compounds also increases. Further, they are compounds which allow ordinary separation/transfer operation such as distillation. In the case of melamine, for example, after the reaction, most part of unreacted melamine precipitates as crystals in the solvent used in the reaction and can be separated by filtration or the like method. On the other hand, the product, most of which is dissolved in the solvent, allows ordinary separation and purification such as solvent extraction or distillation.
An object of the present invention is to provide a method of modifying 1,3,5-triazine derivatives which method can readily prepare substituted 1,3,5-triazine derivatives in high yields, the substituted 1,3,5-triazine derivatives being useful compounds utilized widely as fine chemical intermediates for various agricultural chemicals, medicines, dyes, coatings, and the like or as various resin materials, flame retarding materials, by introducing a substituent into an amino group or a mono-substituted amino group on one or more carbon atoms on the 1,3,5-triazine ring using an alcohol.